Operational cables of bicycles are normally mounted along the outside of the tubular frame members. These cables are used to control both front and back wheel braking capacities and front and back shifting mechanisms such as the front and rear derailleurs.
Disposition of these cables outside of the frames has proven troublesome as the cables are exposed to possible damaging conditions. Also outside mounting of the cables along the tubular frame members sometimes covers the art work or graphics on the bike frame therefore adversely affecting aesthetic appeal characteristics.
Various attempts have been made in the past to thread or house operational cables through bicycle frames. For example, in U.S. Pat. Nos. 4,915,404 and 4,917,397 (Chonan) cables are threaded through tubular frame members. However, in accordance with these disclosures, adequate leeway for fluid drainage through the tubes is not provided for. Accordingly, moisture that enters the tube interior through the openings provided for the cables may cause corrosion problems.
Moreover, the bicycle frame shown in the '404 Chonan patent discloses the use of a cable guide member connected to the bottom bracket. In this disclosure, the cables must be carefully guided through the openings provided in the guide, thus calling for an intricate cable installation process.
Other prior art patents that disclose routing of bicycle cables through the frame tubes include Italian Patent 432825 and U.S. Pat. No. 4,583,755 (of common assignment herewith).
Prior art patents which may be of background interest to the invention include U.S. Pat. Nos. 4,905,541 and 5,269,196.
Despite the efforts of the prior art, there remains a need for a bicycle frame structure that facilitates threading or housing of bicycle operational cables inside the tubular frame members while providing for adequate drainage. There is a specific need for such structure which accomplishes these purposes and allows for easy threading of the cables through the frame tubes without requiring the addition of extra parts.
Further, it is highly desirable to provide a bicycle frame down tube of the type adapted for reception of an operative cable or cables therein that allows for exit of the operational cables at a location spaced below the crank arm assembly bracket so that chances of cable interference with pedalling are reduced.